The Seattle Seahawks and San Francisco 49ers are tied with the Arizona Cardinals for first place in the NFC West, and this division has been characterized by a commitment to tough defense.

All three of the teams at the top are 4-2, while the St. Louis Rams are 3-3. Each NFC West franchise ranks in the top 10 in the NFL in yards allowed. In addition, the Chicago Bears have allowed the fewest points per game in the league, while Seattle, San Francisco, Arizona and St. Louis rank second through fifth in that order.

When the Seahawks and the 49ers face off tonight, defense will decide the winner.

Here are the individual players who will have the largest impact on the game.

NaVorro Bowman, MLB, San Francisco 49ers

While Patrick Willis has received much of the attention in San Francisco this season, NaVorro Bowman is starting to get people talking as well.

The third-year man is playing at an All-Pro level for the second season in a row, and he is third in the NFL with 60 total tackles. Bowman also leads all 49ers with five passes defending and also has an interception.

He has the speed to be a sideline-to-sideline player, and is equally effective against the run as he is in coverage.

The middle linebackers are the heart of San Francisco’s elite defense, and Bowman will have a major impact on the Seahawks offense.

Kyle Terada-US PRESSWIRE

Richard Sherman, CB, Seattle Seahawks

The Seahawks have a big, physical secondary and no defensive back has made as much of an impact for the team this season as Richard Sherman.

The second-year cornerback is tied with the Bears’ Tim Jennings for the NFL lead with 10 passes defended. He is also one of many players tied for third in the league with three interceptions.

At 6’3”, he is an exceptionally tall cornerback and he will not be pushed around by any of the 49ers wide receivers.

Alex Smith is coming off of a three-interception performance against the New York Giants, and if he is not careful this week, he will complete a pass to Sherman.

The Seahawks offense is heavily dependent on Marshawn Lynch and the running game.

San Francisco will head into this game with stopping the run as its top priority, and Justin Smith will lead the effort.

No one in football played the defensive end position in a 3-4 defense better than Smith last season, and with the exception of the Houston Texans' J.J. Watt, no one has been as effective this year either.

Smith is a monster in the trenches, and the Seattle offensive line will have a tough time keeping him from creating problems for Lynch. If Smith can contain the Seahawks running back, the Niners will win this game.

Brandon Mebane, DT, Seattle Seahawks

How many combined point will there be in this game?

15 or less30-1645-31More than 45Submit Votevote to see results

How many combined point will there be in this game?

15 or less

7.7%

30-16

70.2%

45-31

21.2%

More than 45

1.0%

Total votes: 104

The Seahawks rank second in the league in rushing yards allowed per game, and Brandon Mebane has been a significant part of the team’s success.

San Francisco also relies heavily on success in the running game on offense, and if Seattle can shut down Frank Gore, the team will have an excellent chance at victory.

Mebane has been a factor in both stopping the run and rushing passer, and he will need to excel in both areas in order for the Seahawks to earn a victory on the road.

This contest will be won in the trenches, and Mebane will need to dominate along the line of scrimmage on Thursday night.